Event Horizon Telescope, Milky Way supermassive black hole stream

[Orodruin]

Streaming now:

 

[Orodruin]

Sag A* (as seen by EHT):

 

[Orodruin]

Press release:
https://eventhorizontelescope.org/blog/astronomers-reveal-first-image-black-hole-heart-our-galaxy

Special issue of APJ (not yet accessible at time of writing):
https://iopscience.iop.org/journal/2041-8205/page/Focus Issue_on_First_Sgr_A_Results

 

[.Scott]

My expectation was that the accretion disk would have been aligned with the galactic disk.
But it's tilted towards us - mugging for the camera.
There really is no reason it should be aligned to the galactic disk. The accretion disk would be a rather temporary and dynamic structure - with its axis of rotation determined on the entry path of its most recent captures.

 

[Oldman too]

The accretion disk would be a rather temporary and dynamic structure - with its axis of rotation determined on the entry path of its most recent captures.

Would the orbits of S2, S55 and s62 have an effect on the orientation of the accretion disk? I see that s55 has a closest approach to Sag A later this year.

https://iopscience.iop.org/journal/2041-8205/page/Focus_on_First_Sgr_A_Results

 

[94JZA80]

My expectation was that the accretion disk would have been aligned with the galactic disk.
But it's tilted towards us - mugging for the camera.

I don't know that we can make that assessment based on the image alone. After all, the curvature of space time around the BH is so immense that light from the top and bottom sides of the part of the disk that resides behind the BH (light that would normally be eclipsed by said celestial body, blocking our line of sight, were spacetime not so curved in that immediate region) gets bent up and over (and down and under) the event horizon, and directly along our line of sight as observers at a distance, giving it a face-on appearance anyways...

...so without more than just an image, I'm afraid its tough to say at just how much of an angle we're viewing the accretion disk (if we're viewing it at any angle at all). I hope that communicates, as when discussing such things, it can be difficult to convey concepts and ideas without illustrations, particularly animated ones.

 

[.Scott]

I don't know that we can make that assessment based on the image alone. After all, the curvature of space time around the BH is so immense that light from the top and bottom sides of the part of the disk that resides behind the BH (light that would normally be eclipsed by said celestial body, blocking our line of sight, were spacetime not so curved in that immediate region) gets bent up and over (and down and under) the event horizon, and directly along our line of sight as observers at a distance, giving it a face-on appearance anyways...

...so without more than just an image, I'm afraid its tough to say at just how much of an angle we're viewing the accretion disk (if we're viewing it at any angle at all). I hope that communicates, as when discussing such things, it can be difficult to convey concepts and ideas without illustrations, particularly animated ones.

This isn't my assessment and its more than just the "image alone".

This is the assessment made by the team and reported Michael Johnson during the NSF presentation. His specific statement on this at 35:28 in the video. And the method for determining this is described from about 33:00 on - though I would suggest listening to the entire video.

And you're right, it's "tough to say [with authority]", but they did it.

 

[.Scott]

Would the orbits of S2, S55 and s62 have an effect on the orientation of the accretion disk? I see that s55 has a closest approach to Sag A later this year.

https://iopscience.iop.org/journal/2041-8205/page/Focus_on_First_Sgr_A_Results

Well, of course, "an effect" - but how much of an effect. Everything I've heard (including this video) suggests these kinds of estimations are based on a combination of computational models and hefty electric bills. This is true even when no black hole is involved.

Based on the video, they do not know the spin axis of Sag A*. So apparently the Sag A* accretion disk is not so affected by Sag A* tidal forces as to be readily evident. So I would guess that you could use a Newtonian model to come up with a pretty good estimate. The tidal forces of S2, S55, and S62 can impart some angular momentum to the Sag A* disk. Those forces would be proportional to the diameter of the disk but inversely proportional to the to the cube of the distances.

From various wiki pages: S2 (10 to 15 solar masses) gets about as close as 930au, S55 has a periapsis of 246au, and S62 (6.1 solar masses) has a periapsis of about 16au.

 

[atyy]

Did anyone in the USA get a Krispy Kreme donut? They were giving free glazed donuts to celebrate EHT's Sag A* image.